AUSTIN, Texas (Reuters) – Restrictions on voting rights in conservative states endanger the core of the U.S. civil rights movement and force Americans to recreate “a yesterday we’re better off done with,” former President Bill Clinton said on Wednesday.

Speaking to a crowd of students and activists in Austin, Texas, Clinton slammed new voting laws that require photo IDs, make voting harder for students, or otherwise tighten up access to the polls.

“We all know what this is about,” Clinton said at a gathering called the Civil Rights Summit at the Lyndon Baines Johnson presidential library. “This is a way of restricting the franchise after 50 years of expanding it.”

Last year the Justice Department separately sued Texas and North Carolina to block voter-identification laws. Supporters say the laws are needed to combat voter fraud.

Clinton is among four American presidents to address the three-day meeting, joining President Barack Obama, Jimmy Carter and George W. Bush to mark a half century since Johnson signed the landmark 1964 Civil Rights Act.

The Civil Rights Act outlawed discrimination on the basis of race, ethnicity, religion or gender, and was followed a year later by the Voting Rights Act – part of which was struck down by the U.S. Supreme Court in 2013.

Obama is set to speak early Thursday, with Bush to follow in the evening. The gathering also includes discussions by Civil Rights-era figures such as Vernon Jordan, Andrew Young, and Julian Bond.

Johnson ascended to the White House from the vice presidency after the assassination of President John F. Kennedy. While he closed out his administration in 1969 under the cloud of Vietnam, advancing civil rights was his strongest legislative legacy, the gathering’s organizers said.

But the current trend of political divisiveness, clamping down on voting access, and denying undocumented immigrants the opportunity to become voting members of society threatens to undermine all that hard work, Clinton said.

He pointed to himself, Carter and Obama as examples of presidents who would never have been elected were it not for the expansion of voting rights to minorities.

“How could we possibly consider doing anything that would shrink the pool of talent, shrink the scope of personal dignity, shrink the options for people’s achievements?” Clinton said. “It’s just nuts. It doesn’t make any sense.”

(Reporting by Karen Brooks; Editing by Mohammad Zargham)

[Image: Former U.S. President Bill Clinton begins a discussion for the opening plenary session titled “The Age of Participation” on the first day of the 2014 Meeting of the Clinton Global Initiative University at Arizona State University in Tempe, Arizona, March 21, 2014. By Samantha Sais for Reuters]